COLUMBUS, Ohio — There’s a new arms race in the fast food industry: competing to see who can deliver faster and better service to customers pulling up to the takeout window.

With drive-through now representing a huge portion of sales — 70 percent at Burger King Corp. alone — the answer can make or break the fast food giants.

The trick is finding new ways to stand out in an industry ultimately limited by how fast workers can assemble orders, collect payment and hand out food to drivers. Companies are trimming bulky text from menus, using computer programs that guess upcoming orders and routing order-taking duties to call centers.

While speed remains a benchmark of success, the average service time hasn’t been cut much below about three minutes for the last five years. That’s why many chains are focusing instead on cutting down on the number of mistakes in orders and making ordering easier.

“Getting faster and faster and faster isn’t necessarily meeting the experience,” said Mike Watson, vice president of operations at Wendy’s International Inc. “You can go too fast, and then it’s just messy.”

Pam Farber, the daughter of Wendy’s founder Dave Thomas, remembers that when she worked at one of her father’s fast-food stores in the 1970s, customers were often baffled by the drive-through concept. She often had to run outside with a pen and pad to talk to customers who were confused by the bullhorn speaker or whose loud mufflers overwhelmed cashiers’ voices.

Now that unfamiliarity is no longer a problem for consumers hungry for convenience, Wendy’s is replacing some of the text on menus with more pictures and placing awnings over menu boards to shield customers from rain and snow.

Technology firms such as TechKnow Inc. are stepping in with digital menus, used at many major chains, that can increase sales by suggesting “missing” side items or desserts to customers who order only entrees.

And outsourcing is expanding at McDonald’s Corp., where some stores are using central call centers rather than cashiers in the restaurant to take orders from drive-through customers.

Smaller chains, such as Checkers Drive-In Restaurants Inc., have started testing confirmation screens, which display orders back to customers so they can make corrections before pulling up to the window. That technology has helped boost accuracy by more than 11 percentage points in four years at fast-food leader McDonald’s.

Burger King is working to break the speed barrier with its own technology that helps cooks ensure that precooked food remains fresh by keeping track of how long it’s been since it was prepared.

Without such developments, speed will continue to stagnate, said Brian Baker, president of marketing research firm Insula Research, whose clients include Burger King.

“I think we’ve pretty much gotten as fast as we’re getting” with the current technology, said Baker, who wrote part of the 2005 drive-through study for trade publication QSR Magazine. The magazine spot-tests major chains annually to measure drive-through speed and accuracy.

To help cut the waste from leftovers, Pittsburgh-based Hyperactive Technologies developed a computer system that tells managers how much food they need to prepare by counting vehicles in the drive-through line and factoring in demand for current promotions and popular staple items.

The system, called Hyperactive Bob, cuts preparation time and eliminates up to 60 percent of waste, said Joe Porfeli, the company’s chief executive, who said two major national chains use the service. He declined to give their names.

Burger King has started using similar technology, said Jim Hyatt, chief global operations officer of the Miami-based chain. The technology monitors the status of precooked food and determines what orders the kitchen should expect, he said.

Wendy’s, with 9,800 restaurants and $3.2 billion in annual sales, has led the QSR studies for speediest service nearly every year since they started in 1997. But Checkers trimmed that lead to just three-tenths of a second last year with debit and credit payment systems and touch-screen computers for order-takers.

The Tampa, Fla., company, aims to get more orders right as it tests confirmation systems in some Florida restaurants, Chief Executive Keith Sirois said. The effort includes slimming down the menu to simplify order preparation, he said.

Cutting menus is a tried and true way to improve speed as well, said Carl Sibilski, an analyst with Morningstar Inc. who noted that companies rolling out new menu items have had a more difficult time beating the clock.

McDonald’s, with more than 31,000 restaurants worldwide and $20.2 billion in sales, did not return calls. But Sibilski, who follows the chain, said McDonald’s is expanding its use of call centers for taking drive-through orders, to ensure accuracy.

The outsourcing started in the Pacific Northwest and is now taking root in states such as Minnesota, Sibilski said. The system also is helpful in areas where the chain’s employees may have limited English skills, he said.

Amy Pomante, 20, of Oxford in southwest Ohio, said communications with drive-through employees have come a long way. “They haven’t gotten faster, but you can understand them now,” she said as she shopped for groceries in Columbus.

Pomante held her hand in front of her mouth and imitated the garbled speakers she grew up with. “You don’t get that anymore,” she said.

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